The present invention relates to a method for the formation of the actual load angle value for a field-oriented regulated rotating field machine and to a field-oriented regulating device for a converter-fed rotating field machine.
In "Siemens Forschungs- und Entwicklungsberichte", (1972), pages 184 to 193 it is explained that it is advantageous for the regulation of a speed-changeable polyphase machine, in a system of coordinates rotating synchronously with the field axis, to preset a nominal current vector on whose angle then the angle of the rotating field axis is coupled which corresponds to a rotation of the nominal current vector about the field angle, i.e. a transformation of the coordinates from a field-oriented system of coordinates into the stator-oriented system of coordinates. The thereby formed stator-oriented nominal current vector is then impressed on the machine via the converter.
In the case of a voltage-impressing converter, for example, a direct ac converter or an intermediate circuit converter with impressed intermediate circuit dc voltage, it is provided in illustration 16 of the Siemens referral to form from the given nominal current vector in a subsequent decoupling numerical processing unit in the field-oriented system of coordinates the defining quantity of a field-oriented nominal voltage vector which subsequently through appropriate vector rotation is transformed into the stator-oriented system of coordinates in order to supply the stator-oriented nominal voltage values for the converter.
So that the actual current vector corresponding to the fed- in phase currents which can be detected by a current detector connected to the machine coincides with the fieldoriented given nominal current vector, a regulating device is provided which with its nominal value input is connected to the input device for the field-oriented nominal current vector and with its actual value input (via a vector rotator for transformation from stator reference system into the field reference system) to the current detector. In the known case the vector output signal of the regulating device is fed into the decoupling circuit in order to form the nominal voltage vector required for impressing the field-oriented nominal current vector which after transformation in stator coordinates is supplied to the stator-oriented nominal voltage vector for controlling the converter.